Preparation of dioxolanes



June 6, i944. l.. sQulREs 2,350,940

I PREPARATION 0F DIOXOLANES Filed July 24, 1942 4 Con-denser ffafafs/Sf Lombard Squires IM/ENTOR.

ATTORNEY Patente-d June 6, 1944 2 a a PREPARATION OF DIOXOLANES Lombard Squires, Westtown, Pa., assignor to E'. I. duPont de Nemours & Company, Wilmington, Del., a. corporation of Delaware Application July 24, 1942, serial No. 452,249

1sA claims. (o1. 26o-33s) Thisr invention relates to an improved process bing tower and removing the'excess catalyst built for the preparationof organic compounds and up by the discharge of aA portion of the scrubbing moregparticularly'to the preparation of dioxolanes liquid from the primary reaction zones. from vicinal glycolsand formaldehyde, Fig.I III illustrates another apparatusin which A11-.object of the presentinvention is to provide 5 a further and preferred embodiment of the inanv improved processY for` the preparation of Vention can be conducted wherein the features products from vicinal glycols and; formaldehyde illustrated inFigs. I and II are combinedto give,

wherein; loss of 'formaldehyde iszinhibited. Ana process wherein a portion of the scrubbing other object is to provideaprocessfor therecovliquor is regenerated, and recycled and another ery of formaldehyde fromvthe reaction-vapors by portionV purged for removing undesiredmaterials scrubbing the vapors' withv an acidied. glycol or which build up in the primary reaction zone. substitution product thereof; A further and more With reference to Fig. I, the reaction vessel I, specific object is toprovide an .eilicient and'eco- Which-is designated as Atlleprimary reaction zone, nomical process for thev preparation of 1,3-diis charged with Water, glycol. formaldehyde, and oxolane. Other objects and advantages of the 15 arracdic catalyst, the resulting mixture heated inventionVv willi hereinafter appear. andthe product which containsY water, dioxolane In thexpreparation of dioxolanesand more' parand formaldehyde passed'as a vapor into the botticularly 1,3-dioXcl-ane from ethylene glycol, formtom ofthe scrubber 2`wherein itcontacts acoun= aldehyde, and an acidic catalyst,. the 1,3-c`liox-v tercurrent OW- 0f glycol and. sulfuric acid inolane-is usually recovered from the'reaction mix- 20 troduced into'the scrubberv throughv preheater 9. ture by distillation. During the distillation apthefpreheater 9-being uti1i2ed to brine the tem'- preciable quantities of'formaldehyde distill over Default@ 0f the glycoLsulfuric acid mixture to with dioxolane and water and must be recovered the lpcflirllctcY Operating temperature 0f thc if the process is to be eciem; and economical, scrubber 2. WithinY thescrubber and the. regenandgmoreover,v the presence of formaldehydedurcrawl' 5411 formaldehyde present ih the VapOIS ingcondensation results in the formation 0f para.. lfl'OIllvk the reaction Vessel' al@ Substantially all formaldehyde and ultimately in'plugsin condens- COIIVcTicd t0 1,3d0X01aI1c, by What iS callcdthe .g1-Sv and other equipment In accord with this secondaryreaction. Thefreaction products which invention, it has beenfound that if the vapors @OHSS 0f 1,3-d0X0lu1c @JudA a Small amount of` from. the reaction containing, in addition toI difc'mcldchydc'issuc from tllctcp 0f the scrubber` oxolane, formaldehyde and water, are contacted and Dass-11112013116 Condenser 4. From thisv con'-v (by, for example, scrubbing) with an aoidied denser a portionof thecondensed product is sent" ethylene glycol,` substantially all of the-formaldet0 Purifying` ulltS` not Shown and a suicient hyde present in the vapors arenot only absorbed amount reiluxedfor accurate control of the scrub-H in-thisllquid but if the temperature ofthe liquid 3 .bins Operations. The scrubbing liquidv passes isY maintained at the reaction temperature of 'the flQmlh'e bOlftOm OfthcScrubbcf 2'11t0 the regenn Cil vicina] glycopformamehyde to dioxolane Teac, erator 5 wherein it is heated by means not shown non; the dioxolanu win also be formedV iu 'the and the'sreater portion of the-formaldehyde pres' scrubber; entreacts and distills as 1',3dioxo1'ane through The inventioncanbe` more readily understood 40 pPe'b'ntO the bottom 0f` the scrubber 2- The by-reference tomi-attached drawingv `in the figregenerated `scrubbing liquid which comprises esuresof which like partsA are designated by like Senlllly glycol plus a-small amount of sulfuric numerals throughout acidpasses throughzthe cooler'lf, pump 8 and pre- Fig.` IA is` a diagrammatic sketch of apparatus heater 9'back into the top 0f the Scrubbrlg c01- in which can-be conducted oneiembodiment of l-.umn 2J TllcA glycol @Onveriied to 1,3-di0Xolane theinvention characterized bythe regeneration ll'lfhe Icgcuelallcl' 5' iS made up by glycol added of the scrubbing liquid, the-vapors from the re.- thl'ughirllct |01 generation beingy returned tothe bottom of the Anothersfeatureof the process is illustrated by scrubber andthe regenerated liquid being. recy- Fie.-f.I'I,which is'substantially identical with the cled through the scrubber. 5.0' main-*featuresoffthe'process as il1ustrated by Fig.. Fig. IIillustrates an apparatus'in which an em- I .eXceptA that-no regenerationv is provided by` this bodiment of another feature ofthe invention can feature 2u1d=V thcacidi'cd Scubblng glycol iS in'- be conducted wherein the regeneration of the troducedthrough preheater 3 intothe scrubber. scrubbing liquid'illustrated inslig.v I; is replacedby 2. The scrubbing'liquid in lieu of'being passed a method ofl adding acidii'ledglycol to the scrub'- 55. through: a regeneratorflowsdirectly to the reaction vessel I which, in order to prevent the accumulation of excess catalyst, is provided with a purge cycle wherein a portion of the reaction mixture is passed into the purge vessel 9 wherein it is treated with an alkali to remove the acid catalyst, the resulting salt separated and the thus substantially acid-free product returned to the reaction vessel I.

The preferred embodiment of the invention il- Y lustrated by Fig. III is in effect a combination of the features described in Figs. I and II. In this instance the scrubbing liquid from the base of thev scrubber 2 is split two ways, a portion being returned to the reaction vessel l,- another Vportion passed to the regenerator 5. The liquid in regenerator is returned to the scrubber by the route;

described above under a discussion of Fig. I while weight ratio.

.-aration. vThe contents of the reaction vessel l 'wereimaintained between 105 and115 C. at a Vfpressure slightly in excess of atmospheric and KVVthe vapor distilling from this vessel was comthe Vapor is returned to the base of the scrubber 2. A portion of make-up glycol necessary toreact with the formaldehyde charged to I is added, together with a small amount of catalyst, near the top of the scrubber 2 through preheater 3. A portion of the scrubbing liquid passing to reaction vessel I eventually builds up a catalyst excess in thisv vessel which Vrequires the use of Na purge as described inthe discussion of Fig. II to hold the'concentration of catalyst to normal requirements.

The scrubbing of the vapors fromrthe'dioxolane l reaction with the acidiiied ethylene glycol is conducted at a temperature ranging between 50 and 150 C. andpreferably between 90' and 1 20" C. It has been found desirable to pass an ethylene glycol containing from 0.5 to 0.01%y catalyst through the scrubber, and preferably about 0.05% of an acidic catalystsuch 'as sulfuric acid, i the amount of glycol added to the scrubberbeing* preferably equivalent to 0.05 to 0.75 mole permoleof total formaldehyde used and preferably" 0.5 mole per mole of formaldehydeon that basisg The reaction inthe primary and/or secondaryreaction may be conducted under super, sub-,

or atmospheric. pressuresas desired.

`This recovery process is not limited solely V'to f `the preparation' of 1,3-dioXolane from ethylenel glycol and formaldehyde but may likewise be, employed for the preparation of the substitutedv 1-,3-'dioxolanes which are prepared from formal-f' dehyde and vicinal glycols (that is, glycols Ywhichcontain Lhydroxyl vgroups on adjacent carbon atoms),V examples of which are 1,2-propylene' glycol;` 1,2-buty1ene glycol;v 2,3-butylene glycolyj' 1,2-'amylene glycol; 1,2-heigamethyl'ene glycol,` and the like.`V Reactions of this nature, as ls'fV known, are conducted in the presence ofacidic type catalysts such, for example, assulfuric acid,

phosphoric acid, hydrochloric acid, stannic chlo` ride, and the like. The invention `covered her ein, however, is not solely directed to the process per se, but to the scrubbing Vstep andthe secondary reaction thereof, which is preferably carried out with the same vicinal glycoland cata-4" lyst that is used inthe primary reaction to formVV the corresponding dioxolane, although, ofcourse, 1t will be appreciatedthat glycolsv and catalysts? may be used in thisstep of the process which are f dissimilar to those used duringthe primary rereaction taking. placeduring the' scrubbings operation-would give, in theevent that a different isrprepared in the primary reaction.

vicinal glycol is used, a different dioxolane than Y desirable if a conversion between V99 and 100% action. Under such circumstances, howeverg'the Examples will now. be given illustrating'em`vr a bodiments ofthe invention but it willbe understood' that the-invention ,will not be limited by -posed kof 65-67 parts of 1,3-dioXolane, 2-3 parts of formaldehyde and 30-33 parts of Water.

This vapor was injected into the base of a twenty-five' foot scrubber 2 and was passed countercurrent to the iiow. of a scrubbing liquid composed of ethylene glycol containing'from 0.1

to 0.3% sulfuric acid introduced through preheater 9. As'the vapor passed through the scrubber 2, free formaldehyde was absorbed by the scrubbing liquor and reacted with the ethylene glycol thereof, so that the vapor leaving'the top of the scrubber contained a maximum of 0.25

0.35% -free formaldehyde.

- The scrubbing liquid was introduced at the rate of 10-20 partsl thereof per part of the free formaldehyde in the vapor and discharged from the base ofthe scrubber tothe regenerator. While the 'reaction' of formaldehyde with ethylene gly.--

col is rapid, insufficient: contact time is obtained in'rthe scrubberI 2forfequilibrium conversion of absorbed'sformaldehyde toA '1,3-dioXolane. vThe liquoizdischarged from the bottom of the scrubber' 2 therefore, was injected into the regenerator 5 where'it'washeated to 130.C. for a period of from 15:,to 30 minutes average contact time. The Y vapors; from the regenerator 5,were returned to the ,scrubber 2 with theaforementioned reaction'. vapor.r v'Ihe scrubbing liquor composed of from` 0.25.to;0.35 part of freeformaldehyde, 0.1-0.3 partrof; sulfuric acid, `10-12 parts of Water, and 8'7-89 parts of ethylene glycol was passed through the cooler1,'-pump 8, and preheater 9,' back into the scrubber 2. This recycled scrubbing liquor was adjusted to the temperature of the scrubber 100`110F,C. inthe preheater 9 before injection'l into'theV scrubber 2. Sufficient ethylene glycol to compensate for that removed by reaction 4with l free ,formaldehyde in regenerator v5 was added periodically .-to the Ascrubbing liquid through -The^scrubbing operations were synchronized with the reaction operations so that for every -mo1e1of total ethylene glycol added as make-up to the scrubber Zand as a reactant to the reaction'V vessel I-, one mole of formaldehyde was added to the reaction vessel I. This balance is of both vreactants is desired and 'continual ac-r cumulation of excess ethylenelglycol in the reaction vessel is to beavoided.

Example l2;' This example' will be described with reference to Fig. II. f The reaction products from formaldehyde and ethylene glycol obtained in accordwith the chemical yreactionr described. in Example 1 Vwere injected directly into the` scrubber 2 and countercurrent to the downward flow of ethylene glycol acidifled with 0.01 to 0.05% sulfuric acid preheated to c a temperature bebingl liquor, discharged from" the base of" the scrubber, thejliquor`= was-"allowed t'offlovv" directly into'thel reaction vessel` Ivi 'Infthi's reaction ,also

an equimolar balance^was maintainednbetween thejtotal formaldehyde and total ethyleneL glycol added to botl'iscrublciing'fliqi'iidL andzre'a'ction ves'- sel. Since this balafi ".Vlimite'd'theV amount of glycol'which could'v be' injected to the scrubber 2 to to 5 moles of ethylene glycol per mole of free formaldehyde to be removed from the vapor, the distillate removed from the top of the scrubber contains 0.6% free formaldehyde. In this reaction no paraformaldehyde was formed in condenser or tubes.

Although this method eliminated the necessity of regenerating and recycling scrubbing liquor, it introduced a purge requirement to prevent the accumulation of excess sulfuric acid in the reaction vessel. 'I'his purge did not reduce the economy of the process since the purged material could be neutralized and recycled to the reaction. This phase of the process was conducted by bleeding a portion of the reaction mixture from the reaction vessel I to the purging vessel 9 wherein the acid catalyst was neutralized with lime, the calcium sulfate separated and the catalyst-free reactants returned to reaction vessel I.

Example 3.-'I'he apparatus that may be used in conducting this example is illustrated by Fig. III. A combination of the procedures described under Examples 1 and 2 is described by this example which illustrates a very eicient method of removing free formaldehyde from reaction vapors generally and especially from 1,3-dioxolane synthesized from ethylene glycol and formaldehyde.

In the operation of this method the scrubbing liquor removed from the-base of the scrubber 2 was split into two portions. One portion was regenerated as in Example 1 and recycled to the scrubber 2, entering the middle of the tower after being preheated in preheater 9 to a temperature of 100 to 110 C. The amount of scrubbing liquid regenerated and recycled was approximately equal to 10 to 15 parts per part of free formaldehyde contained in the reaction vapor. Near the top of the scrubber 2 through preheater 3 pure ethylene glycol acidied with 0.05% sulfuric acid Was injected as in Example 2.

The reaction vapor entering the bottom of the scrubber 2 first contacts the mixed recycled liquor and acidied ethylene glycol and finally with pure acidied ethylene glycol. By this means, the free formaldehyde in the vapor leaving the top of the scrubber 2 contained a maximum of from 0.02 to 0.10% free formaldehyde, and frequently showed no formaldehyde at all. In this process also no paraformaldehyde was formed.

I claim:

1. In a process for inhibiting the loss of formaldehyde from the vapors of a reaction for the preparation of a dioxolane from a vicinal glycol,

formaldehyde, and an acid catalyst, the step which ff comprises scrubbing the vapors with a vicinal glycol containing the acid catalyst.

2. The process of claim 1 conducted at a temperature above the boiling point of the dioxolanc.

3. In a process for inhibiting the loss of formaldehyde from the vapors of a reaction for the preparation of 1,3-dioxo1ane from ethylene glycol, formaldehyde, and an acid catalyst, the step which comprises scrubbing the vapors with ethylene glycol containing the acid catalyst.

5.7 The process of'claim'conductedl atajtern perature above the boilingfpoint" of 1,3-dioxolarie.-

6L In a process for inhibiting the loss! of' form`4 aldehyde from thev vaporsv of 'areaction yfor the bing liquid containing a vicinal -glycol and sulfuric acid.

7. In a process for inhibiting the loss of formaldehyde from the vapors of a reaction for the preparation of 1,3-dioxolane from ethylene glycol, formaldehyde, and a sulfuric acid catalyst, the step which comprises scrubbing the vapors from the aforesaid reaction with a scrubbing liquid containing ethylene glycol and sulfuric acid.

8. In a process for inhibiting the loss of formaldehyde from the vapors of a reaction for the preparation of 1,3-dioxolane from ethylene glycol, formaldehyde, and a sulfuric acid catalyst, the step which comprises passing the vapors from the aforesaid reaction into a scrubber and therein scrubbing said vapors with a scrubbing liquid comprising ethylene glycol containing from 0.01 to 0.5% sulfuric acid, the scrubbing liquid being recycled.

9. In a process for inhibiting the loss of formaldehyde from the vapors of a reaction for the preparation of 1,3-dioxolane from ethylene glycol, formaldehyde, and an acidic catalyst, the step which comprises scrubbing the vapors with acidied ethylene glycol containing an acidic catalyst, there being employed as scrubbing liquid from 0.05 to 0.75 mole of ethylene glycol per mole of the total formaldehyde used.

10. In a process for the preparation of a dioxolane from formaldehyde and a vicina1 glycol in the presence of an acidic catalyst, the steps which comprise recovering the formaldehyde from the reaction vapors by a scrubbing operation with a glycol scrubbing liquid containing an acidic catalyst, removing the formaldehyde containing scrubbing liquid from the scrubbing operation, converting it to a dioxolane, and returning the substantially formaldehyde-free glycol to the scrubbing operation and scrubbing the said reaction vapors therewith.

11. In a process for the preparation of 1,3-dioxolane from formaldehyde and ethylene glycol in the presence of an acidic catalyst, the steps which comprise recovering the formaldehyde from the reaction vapors by a scrubbing operation with a glycol scrubbing liquid containing an acidic Y catalyst, removing the formaldehyde containing scrubbing liquid from the scrubbing operation, converting it to 1,3-dioxolane, and returning the substantially formaldehyde-free glycol to the scrubbing operation and scrubbing the said reaction vapors therewith.

12. In a process for the preparation of 1,3-dioxolane, the steps which comprise effecting a primary reaction by reacting formaldehyde with ethylene glycol in the presence of an acidic catalyst, recovering the formaldehyde from the reaction vapors by a scrubbing operation with a glycol scrubbing liquid containing an acidic catalyst, transferring the formaldehyde-containing scrubbing liquid from the scrubbing operation to the primary reaction and subsequently removing a part of the primary reactants, separating the catalyst therefrom, and returning them to the primary reaction.

13. In a process for the preparation of 1,3-di- 4.- 'rhe processoff'ciaim :i conducted 'at af terrif-4 Oxolane. the. Vsteps which comprise aeffetng.: a primary reaction byreagtingformaldehyde with ethylene-glycol,` in thefpresenceof 4am acidic c at-Y a1yst, recovering the f oruraldehyie:l from .the reaction vapors by;y a scrubbingoperationy With-,a

glycol scrubbing liquidicontaiinng an acid oat-l to,.1,3dioxo1ane and vaporizing from this DQT,- 10

tion the 1',3.dioxo1ane Ymader thereinreturning the `remaining -s'ubstantially formaldehyde-free glycol-to thefscrubbingoperaton, scrubbing the reaction vapors therewith and passing another portion ofthe formaldehyde containing scruhbm,T liquidY to thelprimery Vreaction-,-separating the catalyst from a. portion of the .primary reaction mixture,and returning thecatalyst-free composition to the reaction mixture.

LQMBARD SQUIRE'S. 

